1. Field of Invention
This invention relates to ultrasonic toothbrushes. More particularly the invention is concerned with improving the efficiency of earlier generation ultrasonic toothbrushes, improving the coupling of the ultrasonic energy to the fluids in the oral cavity, and the teeth and gums of the user.
2. Description of Prior Art
Powered toothbrushes introduced in the 1950 period provided an improvement over manual toothbrushes, particularly so for individuals with limited dexterity.
Numerous unsuccessful attempts were made and disclosed by U.S. Pat. No. 3,335,443 by Parisi, U.S. Pat. No. 3,809,977 by Balamuth et. al., U.S. Pat. No. 4,192,035 by Kuris, and others to develop improved powered toothbrushes by attempting to vibrate the brush head or the bristles by ultrasonic means. None of these attempts utilized ultrasound transducers, they have merely proposed to replace the conventional motorized toothbrushes with a higher speed vibration. They had no effort to generate and couple ultrasonic waves to the teeth and gums.
The state of the art remained unchallenged in the marketplace until the introduction of the first commercially available ultrasonic toothbrush in 1992 based on U.S. Pat. No. 5,138,733 by Bock. Advances followed quickly by U.S. Pat. Nos. 5,369,831 and 5,247,716 also by Bock.
In the Bock patents ultrasound is generated by a piezo electric transducer in the tip of the brush and it is conducted to the teeth and gums of the user through three layers of plastic materials, the tip of the toothbrush handle, the brush head, and the bristles. Consequently, some of the ultrasound energy emitted by the transducer is attenuated by the multiple surface interfaces and plastics between the transducer and the oral cavity.
The art was also enhanced in 1992 by U.S. Pat. Nos. 5,305,492 and 5,378,153 both by Giuliani et. al. These patents basically teach a mechanically vibrating brush head in the sonic frequency range of approximately 250 Hertz. The sonic frequency vibration is generated by a pair of electromagnets vibrating a steel resonator arm, which is pivoted around a torsion pin to provide a lateral vibration to the brush head. The physical vibration of the bristles enhances plaque removal and provides a pleasant feeling and instant feedback to the user, but still does not generate or transmit ultrasonic energy to the teeth and gums.
The next improvement of the state of the art is represented by U.S. Pat. No. 7,269,873 B2 by Brewer et. al., entitled “Ultrasonic Toothbrushes employing an Acoustic Waveguide. U.S. Pat. No. 7,269,873 is essentially a modification of U.S. Pat. No. 5,138,733 by Bock. Brewer provides an improvement in the efficiency of the transmission of the ultrasonic waves from the transducer to the oral cavity by the addition of a waveguide, which is more efficient than the bristles described in U.S. Pat. No. 5,138,733 by Bock. However, the waveguide suggested by Brewer, while provides certain advantages, still attenuates the ultrasonic energy produced by the transducer. U.S. Pat. No. 7,269,873 by Brewer still only discloses an invention wherein the surface interface between the ultrasonic transducer and the waveguide still creates attenuation of ultrasound and the long acoustic waveguide material extending from the ultrasound transducer located within the toothbrush body to the tips of the bristles also significantly attenuates the ultrasound energy from the transducer. Due to these two attenuating mechanisms the ultrasonic waves emitted by the transducer are reduced in efficiency and still does not provide the ultimate performance. In addition, the mechanism of U.S. Pat. No. 7,269,873 became much more complex and more expensive than the one invented by Bock in U.S. Pat. No. 5,138,733.
What has occurred to date is that not withstanding the teachings of the prior art, the ability to provide ultrasonic wave transmission effectively, inexpensively, and easily has remained unsolved.